Industry‐Scalable Interfacial Design for Stabilizing PET‐Cu Current Collectors

Metallized plastic copper (Cu) current collectors (CCs), featuring a sandwich structure with polymer film—typically polyethylene terephthalate (PET)—as substrate and conductive Cu layers on both sides, offer a lighter and cheaper alternative to conventional Cu CC for lithium‐ion batteries (LIBs). However, the instability of PET substrate in commercial carbonate electrolytes leads to Cu||PET interfacial degradation and capacity fading, particularly under high‐temperature operation. Here, we report an industry‐scalable interfacial engineering strategy to stabilize PET substrate by depositing an Al 2 O 3 layer onto the PET substrate surface via roll‐to‐roll physical evaporation (winding speed: 720 m min −1 , substrate width: 2.5 m). The conformal Al 2 O 3 coating acts as a robust physical barrier that effectively suppresses electrolyte‐induced PET substrate decomposition and maintains Cu||PET interfacial integrity during long‐term cycling. The as‐resulting Al 2 O 3 ‐coated PET‐Cu CC (PET@Al 2 O 3 ‐Cu CC) enables 3‐Ah graphite//LiNi 0.5 Co 0.2 Mn 0.3 O 2 pouch cells an 86% capacity retention after 1000 cycles at 45°C—comparable with the cells with commercial Cu CC (86%) and markedly superior to those using PET‐Cu CC (58%). This work establishes a low‐cost and industry‐scalable solution for stabilizing metallized plastic CCs, paving the way toward cost‐efficient and high‐energy LIBs.